Methods, apparatus, systems and articles of manufacture are disclosed selectively generating and storing hashed reference signatures. An example method disclosed herein determining whether watermark coverage of a first media segment satisfies a dropout constraint, the first media segment corresponding to a first monitoring time interval of a media source feed and, when the watermark coverage of the first media segment does not satisfy the dropout constraint hashing first media signatures associated with the first media segment to generate corresponding first hashed signatures and generating first reference data for the first media segment, the first reference data including the first hashed signatures and the first media signatures. The example method further includes, when the watermark coverage of the first media segment satisfies the dropout constraint, generating second reference data for the first media segment, the second reference data including the first media signatures.

Systems and methods are provided for gathering audience measurement data relating to receipt of and/or exposure to audio data by an audience member. Audio data is monitored to detect a monitoring code. Based on detection of the monitoring code, a signature characterizing the audio data is extracted.

Methods and apparatus to identify media content using temporal signal characteristics are disclosed. An example method includes generating a reference signature based on a reference signal corresponding to known media, generating sums based on peaks in a media signal corresponding to media, identifying signal peaks based on the generated sums, generating a second signature based on normalized curve features, wherein the normalized curve features respectively correspond to the identified signal peaks at a corresponding temporal locations of the corresponding signal peak, and determining whether the media signal corresponds to the reference signal based on a comparison of the reference signature and the second signature.

An example apparatus includes a first query processor to obtain a first hash key, first qualifier data and first value data associated with the first hash key, the first value data including a second hash key and a third hash key; a candidate qualifier to use the first value data to prequalify the first hash key as a candidate for subsequent signature processing associated with a first site signature, the candidate qualifier to: determine prequalification of the first hash key is successful in response to a determination that the second hash key matches a second site signature preceding the first site signature in time and that the third hash key matches a third site signature following the first site signature in time; and determine the prequalification of the first hash key is unsuccessful in response to a determination that at least one of the second hash key fails to match the second site signature or the third hash key fails to match the third site signature.

A method and system for determining a current context of a multimedia content element are provided. The method includes receiving at least one multimedia content element from a user device; receiving at least one environmental variable related to the at least one multimedia content element; generating at least one signature for the multimedia content element; determining a context of the at least one multimedia content element based on the at least one contextual parameter; and determining the current context of the at least one multimedia content element based on at least one contextual parameter and the determined context.

Methods and apparatus to verify and/or correct media lineup information are disclosed. Disclosed example apparatus include a comparator to compare media presentation data representative of media output by a set top box to reference data corresponding to a first station to determine whether the media presentation data corresponds to the reference data, the media presentation data collected while the set top box was tuned to a first channel number. The comparator is also to determine a second station that corresponds to the media presentation data when the media presentation data does not correspond to the reference data, and relate the first channel number to the second station to create a second channel map to replace a first channel map that related the first channel number to the first station based on channel lineup information for the set top box.

Methods and apparatus to generate reference signatures are disclosed. An example method includes collecting a first signature for media being presented to a plurality of households; crediting the media when the first signature matches a reference signature in a reference signature database; in response to determining that the first signature does not match a reference signature in the reference signature database and the first signature does not match an unidentified signature in an unknown signature database, storing the first signature in the unknown signature database; in response to determining that a second signature does not match the reference signature in the reference signature database and the second signature matches the unidentified signature in the unknown signature database, and increasing a count associated with the unidentified signature.

In one aspect, an example method to be performed by a vehicle-based media system includes (a) receiving audio content; (b) causing one or more speakers to output the received audio content; (c) using a microphone of the vehicle-based media system to capture the output audio content; (d) identifying reference audio content that has at least a threshold extent of similarity with the captured audio content; (e) identifying visual content based at least on the identified reference audio content; and (f) outputting, via a user interface of the vehicle-based media system, the identified visual content.

A computing system will compare various reference fingerprints each representing a reference media stream broadcast on a different respective known channel, and the computing system will determine that a plurality of the reference fingerprints match each other, thus defining a multi-match group of the matching reference fingerprints. Further, the computing system will determine that a query fingerprint representing a media stream being rendered by a media presentation device matches the multi-match group, thus raising a question of which channel is carrying the media stream that is being rendered by the media presentation device. By considering one or more attributes of the query fingerprint, the server may then disambiguate and thereby determine the channel at issue, and the server may in turn take channel-specific action.

Apparatus, systems, articles of manufacture, and methods to identify and credit media using ratios of media characteristics are disclosed herein. Example methods disclosed herein include determining a first ratio based on a first time interval and a second time interval of a plurality of time intervals of a reference media signature, the reference media signature based on a media signal associated with reference media, respective ones of the plurality of time intervals corresponding to respective adjacent characteristics identified in the media signal. Disclosed example methods also include determining a second ratio based on a third time interval and a fourth time interval of the plurality of time intervals of the reference media signature. Disclosed example methods further include generating a reference ratio signature based on the first and second ratios, the reference ratio signature used to identify the reference media.